In electrohydraulic braking systems, pressure is built up in wheel brakes either directly with the aid of a pressure source, usually in the form of displacement pump devices having pistons, or indirectly by means of a pressure accumulator. These mechatronic systems always include a complex electronic unit, equipped with extensive software, and a complex hydraulic unit, which is based on a hydraulic circuit diagram and ensures correct accommodation, arrangement and connection of a multiplicity of hydraulic and electrohydraulic components which are controlled by the electronic unit in a systematic manner.
The systems concerned must meet multiple requirements. In particular, they must be able to deal with novel application events with the required reliability. Small size and low weight are always aimed for. Operating feel, and in particular operating comfort with regard to noise and pulsation, are to be improved, since, according to tendency, the frequency of actuation of the hydraulic unit is increasing and the noise level in the vehicle interior is being lowered, especially when electric drives are used. The system must be compatible with hybrid drive systems, while reliable, large-volume manufacture, ultimately enabling the system to be marketed profitably, must nevertheless be possible.
Known from WO 2004/031013 A1, which is incorporated by reference, is a hydraulic unit for slip-controlled braking systems which has three piston-type pumping devices which are integrated in a receiving body for rows of electrohydraulic valves. Proposals are made for improving a hydraulic unit with a plurality of pumping devices of the type specified in such a manner that said unit is suitable for use in electrohydraulic braking systems, with efficient utilization of the installation space within the receiving body and with little operating noise. For this purpose the receiving bores for the pumping devices are integrated regularly at an angle of 120° to one another and in a particular relationship to the receiving bores for valve rows. The configuration is capable of improvement and the document contains no indications of the implementation of more than three pumping devices in the receiving body.
In order to combine reduced pulsation effects with a six-piston pump for a vehicle braking system which is simple to manufacture, there is proposed according to WO 2005/050015 A1, which is incorporated by reference, a section-plane based distribution of pumping devices bundled in groups, which are driven by means of two eccentrics which are axially spaced and phase-offset with respect to one another in a circumferential direction. Two pumping devices arranged in a first section plane of the receiving body form, together with a further pump unit arranged in a section plane offset parallel thereto, a common pressure source for supplying a hydraulic circuit of the vehicle braking system. A further such grouping of pumping devices is provided to supply a second hydraulic circuit. The phase-offset positive control of the pumping devices is configured in such a way that pulsation fluctuations can hardly be felt on the suction side. This compensation of pulsations by means of positive control by two eccentrics is achieved at the expense of positioning the receiving bores for the six pump units with irregular reciprocal spacing of their angles of rotation. Although this has the advantage in principle that only two receiving bores for pumping devices are not disposed parallel to a vertical or horizontal of the receiving body, nevertheless such prioritized treatment of the receiving bores for the pumping devices produces a spatially less economical positioning of the remaining components. This way of proceeding suffers, to a degree, from the disadvantage that all the other components, with their associated connecting channels, must be designed around the receiving bores of the pumping devices. This gives rise to correspondingly high cost and complexity of the drilling technology. This applies in particular to the bundling into groups of respective connections to a pressure path and to a suction path, the particular connection requiring a very large number of bore sections which must open into the receiving body from very diverse sides and must cross multiple times. One pressure path, in particular, comprises no fewer than five individual channel sections (36a-36e).